Various pollsters give Democrats a pretty good chance of getting control of the House of Representatives next year, with an outside chance of the Senate as well. Many Democrats are expecting a complete reversal of Trump-Republican policies. This is at best naïve and at worst displays gross ignorance of our system of government.

I don’t wish to rain on the Democrats’ parade, but they must remember that either Donald Trump or Mike Pence will be president until January 20, 2021. All presidents have veto power and enacting legislation over a veto requires a two-thirds majority in both houses of Congress, something Democrats will not have.

Moreover, Democrats’ odds of getting the Senate this cycle are small and their House majority, should they get it, is likely to be slim. Nor are Democrats united on an agenda or their leadership going forward. The issues their candidates for the 2020 Democratic presidential nomination are likely to make will make the achievement of consensus difficult.

This is not to say that there is nothing Democrats can do even with just House control. But they must dampen expectations lest their base become dispirited by their failure to achieve much of anything, legislatively, until at least 2021.

I have some insight on this because I worked in the Senate after Republicans unexpectedly won control in the 1980 elections. Since Democrats still had solid control of the House, bipartisanship was baked in the cake, although at least we didn’t have to worry about a presidential veto.

Moreover, I was still a Republican in 1994 (I’m now an independent) and was involved in planning the GOP agenda in Congress after the Republican takeover that year. Then as now, many activists needed to be reminded that there was a president of the opposite party and his veto pen was full of ink.

Based on my experience, here is a realistic scenario.

First, Democrats can and should investigate Trump and all the corruption among his cabinet and subcabinet that Republicans have turned a blind eye to. But they should not delude themselves that it will be easy. The administration will stonewall and try to run out the clock. Moreover, thanks to Republican budget cuts, Congress lacks the staff and resources to do the kinds of investigations that were done in the past. Republicans in the Senate will block efforts to provide additional resources.

Democrats will have to dampen expectations.

Second, Democrats need to find some way of chilling demands for impeachment without angering their base too much. While Trump certainly deserves impeachment, the chances of a Senate conviction are zero and the effort will waste a lot of time and energy. Anyway, removing Trump would just make Pence president. From a policy point of view, nothing will change.

Third, Democrats should have the Joint Committee on Taxation obtain all of Trump’s tax returns and review them thoroughly. It already has the legal authority to do this. But Democrats should not expect a smoking gun. The returns themselves may say little without also seeing the supporting data and documentation that the IRS itself only sees in an audit. Also, privacy laws will still apply and it will take much time for the returns to be analyzed.

Fourth, Democrats can make a down payment on restoring funds for programs that have been slashed by the GOP. But Republican control of the Senate will limit what can be done and Trump has made clear that he has no fear of the political consequences of a government shutdown resulting from vetoing appropriations bills.

The biggest problem Democrats will have is dealing with the budgetary time bomb Republicans have planted with their tax cut.

Fifth, Democrats can do a lot to put meat on the bones of an agenda their nominee can run on in 2020. Hearings must be held, speeches given and reports written detailing potentially popular Democratic ideas such as Medicare for All. Democrats must remember that they will be held to a much higher standard by the media than Republicans have. Democrats are the party of responsibility and must bear a burden for that.

The biggest problem I foresee Democrats having is dealing with the budgetary time bomb that Republicans have planted with their tax cut. It is absolutely guaranteed that Republican hypocrites and media scolds will demand immediate action on the deficit as soon as the new Congress convenes. Enough Democrats and their Wall Street contributors will agree to force action.

Republicans will insist, of course, that 100 percent of deficit reduction be done on the spending side. Their long-term goal has always been to force Democrats to cut programs like Social Security and Medicare so that Republicans don’t bear the blame.

Republicans will also insist that, even with the tax cut, revenues are more than adequate to fund the federal government. They will ignore the fact that the major driver of long-term spending is interest on the debt resulting from tax cuts with no reduction in spending, wars without end and trillions for militarily dubious high-tech weapons systems and unfunded Republican programs like Medicare Part D.

Needless to say, tax increases will be off the table. The only person Republicans fear as much as Trump is Grover Norquist, whose no tax pledge guarantees defeat for any Republican who supports even the most modest tax increase. (Apparently, tariffs are okay.) Any tax increases Democrats manage to achieve will be small and grossly inadequate to our fiscal needs.

It is likely that macroeconomic conditions will also force Democrats into the trench warfare of deficit reduction. Inflation has been well-behaved for a long time, but Republicans just added a huge dose of fiscal stimulus to an economy that was already running on all cylinders. Historically, this has been a recipe for inflation. Moreover, the Federal Reserve will continue raising interest rates. While this should theoretically dampen inflation, it will nevertheless make the deficit a more salient political issue. It will be easy for politicians to sell Americans on the idea that interest rates are rising due to deficits rather than Fed policy.

Democrats will find themselves between a rock and a hard place – between demands for action from their base that cannot be fulfilled and enormous pressure to reduce deficits without any help from tax policy.

It is possible that Democrats may keep their base under control with some symbolic victories – getting Trump’s tax returns would be a big one. Robert Mueller’s investigation will continue and presumably deliver more indictments and convictions. Hearings will provide forums for Democrats to highlight Republican corruption and the deleterious effects of their policies. By the end of next year all eyes will turn to the run for the White House. This should give Democrats the leeway to do little substantively without depressing their base too much. The real action will come in 2021.